D shorting diodes controlling a transmission line electrical length single sideband generator employing a plurality of cyclically switche

ABSTRACT

A digital single sideband generator in which the carrier frequency is fed via a circulator to a (microstrip) transmission line which has a series of switchable short circuits (RF grounded diodes) along a length of the line equal to half the carrier wavelength. Successive cyclic switching of the diodes simulates a moving RF energy reflector advancing or retarding the phase of the reflected energy according to direction of switching and resulting in a frequency offset at the circulator output determined by the cyclic rate.

O Umted States Patent 11 1 1111 3,757,222 Oberbury 1 1 Sept. 4, 1973[541 SINGLE SIDEBAND GENERATOR 2,872,647 2/1959 Smith 332/45 EMPLOYING APLURALTY 21%;???) 31323 Q l "332/ 123 ac ey CYCLICALLY SWITCHED SHORTING3,110,862 11/1963 Chasek 325 49 DIODES CONTROLLING A TRANSMISSION LINEELECTRICAL LENGTH P E Alb M rimqry xaminer H ert J. ayer [75 1 Inventorgg 'g gi g gzgg Attorney-C. Cornell Remsen, Jr., Thomas E. Kristoffersonet al. [73] Assignee: International Standard Electric Corporation, NewYork, N.Y. [5 7] ABSTRACT [22] Filed: 1971 A digital single sidebandgenerator in which the carrier [21 1 A No. 216,982 frequency is fed viaa circulator to a (microstrip) transmission line which has a series ofswitchable short circuits (RF grounded diodes) along a length of theline [2%] 3291:8535/2; equal to half the carrier wavelengthsuccessivecyclic 49 switching of the diodes simulates a moving RF energyI 1 2: 3;; 44 2 1 reflector advancing or retarding the phase of the relflected energy according to direction of switching and resulting in afrequency offset at the circulator output [56] References Citeddetermined by the cyclic rate.

UNITED STATES PATENTS 3,437,957 4/1969 Ames 325/138 5 Claims, 1 DrawingFigure SINGLE SIDEIBAND GENERATOR EMPLOYING A PLURALITY OF CYCLICALLYSWITCI-IED SHORTING DIODES CONTROLLING A TRANSMISSION LINE ELECTRICALLENGTH BACKGROUND OF THE INVENTION 1. Field of the Invention Theinvention relates generally to radio frequency systems and, moreparticularly, to single sideband generation.

2, Description of the Prior Art In the prior art there have been variousmethods of obtaining electrical sidebands, including single sidebands.These methods have been either wholly electrical or partiallymechanical, however, many have been complex, lossy or suitable over onlya relatively narrow range of frequencies.

SUMMARY or THE INVENTION It may be said to have been the generalobjective of the present invention to produce a single sidebandgenerator which inherently generates only an upper or a lower sideband,basically substantially lossless, except for a relatively smallcirculator loss, and adaptable to instrumentation over a broad range offrequencies.

According to the invention, there is provided a single sidebandgenerating device including a radio frequency transmission line havingan electical length from one end thereof at least equal to half thecarrier wavelength means for simulating cyclic unidirectional movementalong said transmission line over a length thereof equal to said halfwavelength of a radio frequency energy reflector in a direction and at arate determining respectively the sense and the magnitude of frequencyoffset of the sideband frequency from the carrier frequency, andcirculator means for coupling a source of carrier frequency whenconnected to the circulator input to said one end of the transmissionline and for coupling the reflected energy from said one end of thetransmission line to the circulator output.

BRIEF DESCRIPTION OF DRAWINGS diagram of a system in accordance with theinvention.

DESCRIPTION OF THE PREFERREDv EMBODIMENT A preferred embodiment of theinvention will now be described with reference to the accompanyingdrawing which shows a single sideband generating device.

A radio frequency microstrip transmission line 1 is coupled at one endto an intermediate port of a circulator 2 having an input port 3 forconnection to a carrier frequency source and an output port 4 forconnection to a load.

Connected to the transmission line I along an electrical length d equalto half the wavelength of the carrier frequency are n diodes 5 with anelectrical length spacing of 11/11 between adjacent diodes.

Each diode is connected to ground for radio frequency energy, via asuitable capacitance, shown as a capacitor 6, on application to thediode of a positive switching pulse via each pulse input (typically 7).

There is a pulse distributor 8 for applying the switching pulsecyclically in turn to each of the diodes 5 to enable the short circuitresulting from the respective diode being RF grounded.

of the sideband and the sense of the offset from the carrier frequency.

The energy propagating along the transmission line is reflected at theinstantaneous position of the short circuit to return along the lengththereof, after having travelled a distance determined by the position ofthe short circuit and is thereafter routed from the circulator end ofthe line to the output 4 of the circulator, which prevents the reflectedenergy returning to the source.

Successive switching of the position of the short circuit on the line,typically by a series of 16 diodes (typically 5), causes a correspondingadvance or retard of the phase of the signal at the load, in digitalsteps, determined by the direction of the switching sequence, the shiftin this Signal frequency from that of the carrier being determined bythe rate of simulated movement of the radio frequency energy reflectingshort circuit. After a complete cycle of phase has been introduced(after a half wavelength due to the double path to he travelled),switching reverts to the start for the next cycle in the repetitiveseries.

The above described sideband generator is very suitable for frequenciesbetween 50 MHZ and 3,000 MHZ. Only an upper or a lower sideband isfundamentally generated, and there is'no basic loss other than that inthe circulator.

Modifications and variations falling within the spirit of the inventionwill suggest themselves to those skilled in this art. Accordingly, it isnot intended that the drawing or this description should be regarded asa limitation on the scope of the invention, these being typical andillustrative only.

What is claimed is l. A single sideband generating device for a radiofrequency system, comprising:

a radio frequency transmission line having an electrical length at leastequal to one half wavelength at the carrier frequency;

a radio frequency circulator having input, output and intermediateports, said intermediate port being connected to a first end of saidtransmission line and said input and output ports providing carrierinput and output, respectively;

a plurality of electrically controllable shorting devices spaced along ahalf carrier wavelength of said transmission line;

and means for cyclically controlling said shorting devices to produceshort circuits to ground at corresponding locations progressively alongthe length of said transmission line, thereby to provide a variableradio frequency reflection point for energy entering said line from saidintermediate circulator port, said cyclical control being at a rate andin a sensecorresponding to the desired magnitude of sideband, frequencyoffset from said carrier and the sense of said sideband frequencyoffset, respectively.

shorting devices include diodes responsive to said cyclical control,said means for cyclically controlling comprising an electrical pulsedistributor to produce said electrical sequencing.

4. Apparatus according to claim 1 in which said transmission line is amicrostrip transmission line.

5. Apparatus according to claim 4 including a matched load connected tothe second end of said transmission line for terminating said line.

1. A single sideband generating device for a radio frequency system,comprising: a radio frequency transmission line having an electricallength at least equal to one half wavelength at the carrier frequency; aradio frequency circulator having input, output and intermediate ports,said intermediate port being connected to a first end of saidtransmission line and said input and output ports providing carrierinput and output, respectively; a plurality of electrically controllableshorting devices spaced along a half carrier wavelength of saidtransmission line; and means for cyclically controlling said shortingdevices to produce short circuits to ground at corresponding locationsprogressively along the length of said transmission line, thereby toprovide a variable radio frequency reflection point for energy enteringsaid line from said intermediate circulator port, said cyclical controlbeing at a rate and in a sense corresponding to the desired magnitude ofsideband frequency offset from said carrier and the sense of saidsideband frequency offset, respectively.
 2. Apparatus according to claim1 in which said shorting devices comprise a plurality of normally opendevices equally spaced along said half wavelength and said means forcyclically controlling comprises means for electrically sequencing saidshorting devices to cause them to provide said short circuits to ground,one at a time, said sequencing proceeding in a direction along said lineand at a rate corresponding, respectively, to the desired sense andmagnitude of said sideband frequency offset.
 3. Apparatus according toclaim 2 in which said shorting devices include diodes responsive to saidcyclical control, said means for cyclically controlling comprising anelectricAl pulse distributor to produce said electrical sequencing. 4.Apparatus according to claim 1 in which said transmission line is amicrostrip transmission line.
 5. Apparatus according to claim 4including a matched load connected to the second end of saidtransmission line for terminating said line.